In this study, spray-coating has been opted to prepare patterned Poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes for an organic thin film transistor (OTFT). The conducting polymer was grown via the vapor phase polymerization (VPP) method. The film quality of VPP-PEDOT critically relies on the uniformity of oxidant film selectively patterned on a thermally oxidized Si-wafer surface prior to the polymerization. Therefore, to improve the uniformity of the oxidant film, this study tried to discover best conditions of spray-coating. Several different temperatures of Si-wafer substrate, distances from nozzle to wafer, and spray times were tested during the spray coating process. Then, sprayed oxidant films and vapor phase-polymerized PEDOT patterns were characterized by several thin film analyzing tools such as FE-SEM and optical microscope. The characterization found that the best conditions of spray coating are room temperature, 18 cm, and 50s of substrate temperature, spray distance, and time, respectively. (C) 2014 Elsevier Ltd. All rights reserved.